Process for making a heavy fuel oil with recycle visbreaking of gas oil



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MMM/M TTORNEY Feb- 8, 1966 cHlA-wEl CHEN PROCESS FOR MAKING A HEAVY FUEL OIL WITH RECYCLE VISBREAKING 0F GAS OIL Filed June 20, 1962 United States Patent O 3,234,118 PROCESS FOR MAKING A HEAVY FUEL OIL WITH RECYCLE VISBREAKING F GAS OIL Chia-Wei Chen, Freeport, N.Y., assignor to Foster Wheeler Corporation, New York, N.Y., a corporation of New York Filed June 20, 1962, Ser. No. 203,993 Claims. (Cl. 208-93) This invention relates to recycle visbreaking of gas oil for the production of heavy fuel oil. A simplied recycle system and a process amenable to this system are offered.

In recycle visbreaking systems, heavy Ifuel oil is blended from vacuum pitch, thermal tar and a light cycle oi-l cut from visbroken gas oil. Thermal cracking or visbreaking produces a lower pour point temperature, a lower fluidity temperature and lower viscosity.

A conventional scheme for visbreaking gas oil cut from reduced crude involves the following steps:

(A) Heating and dividing reduced crude -oil under a vacuum to produce a gas oil portion and bottoms which include vacuum pitch and thermal tar.

(B) Removing the bottoms for blending in a product heavy fuel oil.

(C) Visbreaking the gas oil portion in a thermal cracking zone.

(D) Dividing the visbroken gas oil to produce a top cut, an 4intermediate cut and a residue; with the top cut including gasoline and lighter materials; with the intermediate cut comprising light cycle oil; and with the residue including heavy gas oil and tar.

(E) Removing the intermediate cut vfor blending in the product heavy fuel oil.

(F) Dividing the residue under a vacuum to produce a gas oil portion and bottoms.

(G) Removing the bottoms for blending in the product heavy fuel oil.

(H) Recycling the portion of gas oil to the thermal cracking zone for visbreaking.

The present invention contemplates using the same vacuum asher for Steps A and F. Toward this objective, the residue of Step D is recycled t-o the vacuum flasher used Ifor Step A.

Basically this -advance eliminates one vacuum flasher and often one heater. Energy balance opportunities are lalso presented with consequent utility savings.

These and other advantages will appear more fully from the accompanying idealized drawing of a system embodying the present invention. All of the 'equipment elements per se are well known to petroleum refineries and except for the novelty here indicated the process is known.

In the drawing, reduced crude oil is delivered from atmospheric unit 1 via Iline 2 to heater 3. From heater 3 the crude oil is passed via line 4 to vacuum flasher 6 wherein the `above-mentioned Step A is completed producing gas oil which exits through line 7. The remainder of the feed constitutes bottoms and is exhausted via bottom line 8 as vacuum'pitch and thermal tar. To accomplish Step B, line 8 transmits the vacuum pitch and thermal tar to product blender 9 wherein it becomes part of a heavy lfuel oil product.

Step C calls for directly visbreaking the gas oil. Line 7 communicates the gas oil to thermal crack-ing furnace 11 wherein it is visbroken to give it a lower pour point temperature, a lower fluidity temperature and reduced viscosity. By directly it is meant, free of intermediate process steps.

Division according to Step D is performed in fractiona- 3 ,234,1 i8 Patented Feb. 8, 1966 ICE 4 tor 1'2. Eiiluent from thermal cracking furnace 11 passes via line 13 directly to fractionator 12 wherein the visbroken gas oil is divided into .a top cut which exits via line 14, an intermediate cut which exits via line 16 and resldue which exits via line 1-7. The top cut includes gasoline and lighter materials. The intermediate cut comprises light cycle oil. The residue includes heavy gas oil and heavier materials. i

Line 16 passes light Icycle oil to blender 9 for Step E.

The crux of the present teaching is to use vacuum asher 6 `for both Steps A and F simultaneously. To accomplish Step F -line `17 recycles residue from fractionator 1-2 to flasher 6 wherein additional gas oil is produced for visbreaking. Depending upon the temperature of the gas oil cut Ito be made in Step F, all or 1a `porti-on of fthe residue recycled via line 1'7 may be passed through heater 3.

For control of recycle to vacuum flasher 6 it is often desirable to draw olf a portion of the residue. Accordingly line 17 is connected to product blender 9 via line blender 9 is accomplished by line 8 which also accomplishes Step B.

This system is especially suitable for light crudes such as those from the Sahara Desert. These crudes tend toward instability of heavy fuel oil. "A representative Sahara crude is characterized in TableI. In- Table II this process is compared with a conventional two-pass visbreaking process. The upper portion of Table II presents results obtained when residue is recycled via line 17 to upstream of heater 3. The lower side of Table II relates comparable results for the same crude visbroken according to the conventional process. lt should be noted that pour point temperature is lower with the present process. Also the difference between the bottom sediment and water before and after oxidation is a commercially acceptable 0.3 as compared to a woefully unstable 2.85 by the conventional process.

It will be apparent that wide changes may be made in tjhe details of the shown embodiment without departing from the spirit of invention set forth in the claims.

TABLEII Heavy fuel oil production [With residue from iractionatdrsrecycled to vacuum asher] f @Olli/950 Heavy Fuel J Product h Charge Oil -Frorn V-Iiteavy'liuel l v Vacuum First `Pass. Oil

Gas Oil @aeration Gravity, API, 2o. 7 19. 9 Viscosity, SSII, at-

100 F 474 319 150 F 120:5 '10114 21091? Pour Point, F -60 44 5 Stability:

BSW `before 02 0. 2 l 0. 2 BSWaiter 02 0. 35 `0. 5

[With first vacuum,flashenaudlrecyle-fmmsecond-vacuum flasher] Charge.` Heavyaluel.; Product Reduced Oil Erom Heavy .Crude :First Pass f Fuel Oil operati@ w Gyayiy, APL, 4 I22,14 i 21. 3

100 250. 6' 180: 8 198. 0 89.y 0 7D; 5 .L21OF 75.0 Pour Point, 100 v70 "60 Stability:

` BSW-before Oz 0. 7 0. 25 0. 15

nsw-after o2 0.8 4.170 3.o

TABLE 1.11

. Testmethod TestV p .Method Gravity, AP1 ASTM D-2s75'5. Viscosity/,Saybolt .Universal ASTM D-8 8-56.V Pour'Point A ASTMD`-97,-` 5"7. X Fluidity at 32 F; Mil-FT8559EH56.v Stabilityf 1- veve-=e-s UOPf-F-l74-52-.f

What isrclaimed is:

`1,. A process for producing heavy fuel oil from lreducedcmdeoil Comprising the Steps 0f,

heatingatmospheric reduced crude; oil,

dening a single fractionatingzone,

passing the atmospheric `reduced crude oil through i. the single fractionating zone, to produce` a fgas:.oil=` portion and bottoms, Y

passing directly thegasl oil portionto a `thermalcraclg- Y ing l zone for` thermal. cracking therein,

passing directly ,the thermally cracked gas oil :to a frac-p -tionator zone for division to,producea residue .of they thermally .cracked gas oil` including a heavy gas oil and heavier materials,

Vrecycling vthe residue to thesingle fractionating zone for fractionatiomtoget-her-'with the atmospheric reduced crude oil,

'lt-.he single fraetionating zone further producing residue bottoms from the residue,

removing .the vbottoms VVandf-the residuey ubottoms together `from. the. .single fractionating zone,

, blending .thelbottomsandresiduebottoms `with alight oil fraction to produce heavy fuel oil.

2.l A process for producing heavy fuel oil from reduced crude oil comprising the steps of,

4; refining a s'iu'gle 4heating zone ing zone,.

passing atmospheric reduced crude oil serially through vthe single heating zone andthe single fractionating zone to producen gas oil portiouand bottoms, passing directly thegas oil Vportion to .a thermal cracking zone ,fon thermal crack-ing therein,-

oil and heavier materials, Y

recycling'giheresidue ,directly to theuzsin'gle heating zone and. the Lsingle ractionating @zone rior fractionation =together with the atmospheric 'reduced` crude oil,

-the singleifractionating zon'eturth'er producing residue bottoms from fthe' residue, removing the bottomsand the residue bottomstogether fromzthe'single fractiohatingzoneg:

iending`the-bottoms Iand-residue `bo'ttornsfwith a light` :oil fracton :to produce `heavy l fuel `oil.

3. A vprocessY for l producing VLVheavy fuel z oil from re` duced lcrude ,oil comprisinghe steps of', A ."delining a single heating 1zone anday singlefractionat;

ing zone, v passing @atmospheric` reduced Acrude oi'lfserial-lythrough `t-he. singlelheating-.zone and fthe Vsingle",frac'ztionating zone to producea ygasp-oil portion and fbottoms, zpassingrrdirectlythegas oil @portionto a thermal cracking zoneforthermal cracking therein,

vpassing directly; theftherrnal-lyg cracked igas loil `to a fractionator-zonefor-division to produce .a :residue of the Vtliermally`c15acked gas oil and :a :top cut and an` intermediate' cut,m said topcut including gasoline andY lightermaterials,`-

irecycl-ing'fth: residues-directly to .the single heating g.

zone and fthe single `tractionat'ing zone for fraction-V` ationitogethrwitli the atmospheric)reducedlcrude'VV the singler i fractionating zone f further producing residue bottoms from ythe residue,

' removin'gthcibo from the single ,fractionating zoneg n'-ble'uding fthe bottomsr-and-residue; bottomswith la light oilfactionetoproduce heavy fueloill." p :Theaproce'ssof claiml 3 5with thefintermedia'te cut comprising lightcycle oil; andwherein theflight oil lfracf ktionblended with'vthe `bottoms and residuebottoms corn-V prises said intermediate eut.

5.-.The proces'srfof=.clain1 4-vvith the fractionating zone operatediunder subatrnospheric pressure..

UNTi-znssfrarns :PATENTS 2,633,449;V 3/1953. Cheneyg .,20s 76 v2,651,60119/1953 .Taft etai 20:;94 2,663,675 12/1953 Ewen 20s- 73 2,717,856` 9./1955 RamasV eral., 20a- 15 3,110,66511'11/1953 Minen 20s-@93 DELBERT iE. ffGANlz, Primary Ex'amner.` ALPHQNSD D.4 `SULLIVAN IExamirrer; ILI.` LEVI-NB', "Assistant Examiner;

. and a singlefractionat-y ttoms and the residue bottoms together.`

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3 ,234 ,118 February 8 1966 Chia-Wei Chen It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, 1ine 1, for "refining" read defining line 10, after "heavy" insert gas Signed and sealed this 7th day of February 1967 (SEAL) Attest:

ERNEST W. SW'IDER Attestng Officer EDWARD J. BRENNER Commissioner of Patents 

1. A PROCESS FOR PRODUCING HEAVY FUEL OIL FROMREDUCED CRUDE OIL COMPRISING THE STEPS OF, HEATING ATMOSPHERIC REDUCED CRUDE OIL, DEFINING A SINGLE FRACTIONATING ZONE, PASSING THE ATMOSPHERIC REDUCED CRUDE OIL THROUGH THE SINGLE FRACTIONATING ZONE TO PRODUCE A GAS OIL PORTION AND BOTTOMS, RECYCLING THE RESIDUE TO THE SINGLE FRACTIONATING ZONE FOR FRACTIONATION TOGETHER WITH THE ATMOSPHERIC REDUCED CRUDE OIL, THE SINGLE FRACTIONATING ZONE FURTHR PRODUCING RESI DUE BOTTOMS FROM THE RESIDUE, REMOVING THE BOTTOMS AND THE RESIDUE BOTTOMS TOGETHER FROM THE SINGLE FRACTIONATING ZONE, BLENDING THE BOTTOMS AND RESIDUE BOTTOMS WITH A LIGHT OIL FRACTION TO PRODUCE HEAVY FUEL OIL. 